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Message-Id: <1322685846-7790-2-git-send-email-sjur.brandeland@stericsson.com>
Date: Wed, 30 Nov 2011 21:44:04 +0100
From: Sjur Brndeland <sjur.brandeland@...ricsson.com>
To: netdev@...r.kernel.org
Cc: David Miller <davem@...emloft.net>,
Alexey Orishko <alexey.orishko@...ricsson.com>,
Sjur Brændeland <sjur.brandeland@...ricsson.com>
Subject: [RFC 1/3] caif: Add support for flow-control on device's tx-queue
From: Sjur Brændeland <sjur.brandeland@...ricsson.com>
Flow control is implemented by inspecting the qdisc queue length
in order to detect potential overflow on the TX queue. When a threshold
is reached flow-off is sent upwards in the CAIF stack. At the same time
the skb->destructor is hi-jacked in order to detect when the last packet
put on queue is consumed. When this "hi-jacked" packet is consumed, flow-on
is sent upwards in the CAIF stack.
Signed-off-by: Sjur Brændeland <sjur.brandeland@...ricsson.com>
---
net/caif/caif_dev.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 48 insertions(+), 0 deletions(-)
diff --git a/net/caif/caif_dev.c b/net/caif/caif_dev.c
index f7e8c70..415353e 100644
--- a/net/caif/caif_dev.c
+++ b/net/caif/caif_dev.c
@@ -34,6 +34,7 @@ struct caif_device_entry {
struct list_head list;
struct net_device *netdev;
int __percpu *pcpu_refcnt;
+ bool xoff;
};
struct caif_device_entry_list {
@@ -48,6 +49,7 @@ struct caif_net {
};
static int caif_net_id;
+static int q_high = 50; /* Percent */
struct cfcnfg *get_cfcnfg(struct net *net)
{
@@ -126,9 +128,28 @@ static struct caif_device_entry *caif_get(struct net_device *dev)
return NULL;
}
+void caif_flow_cb(struct sk_buff *skb)
+{
+ struct caif_device_entry *caifd;
+ WARN_ON(skb->dev == NULL);
+
+ rcu_read_lock();
+ caifd = caif_get(skb->dev);
+ caifd->xoff = 0;
+ caifd_hold(caifd);
+ rcu_read_unlock();
+
+ caifd->layer.up->
+ ctrlcmd(caifd->layer.up,
+ _CAIF_CTRLCMD_PHYIF_FLOW_ON_IND,
+ caifd->layer.id);
+ caifd_put(caifd);
+}
+
static int transmit(struct cflayer *layer, struct cfpkt *pkt)
{
int err;
+ struct caif_dev_common *caifdev;
struct caif_device_entry *caifd =
container_of(layer, struct caif_device_entry, layer);
struct sk_buff *skb;
@@ -137,6 +158,33 @@ static int transmit(struct cflayer *layer, struct cfpkt *pkt)
skb->dev = caifd->netdev;
skb_reset_network_header(skb);
skb->protocol = htons(ETH_P_CAIF);
+ caifdev = netdev_priv(caifd->netdev);
+
+ if (caifdev->flowctrl == NULL && caifd->netdev->tx_queue_len > 0 &&
+ !caifd->xoff) {
+ struct netdev_queue *txq;
+ int high;
+
+ txq = netdev_get_tx_queue(skb->dev, 0);
+ high = (caifd->netdev->tx_queue_len * q_high) / 100;
+
+ /* If we run with a TX queue, check if the queue is too long*/
+ if (netif_queue_stopped(caifd->netdev) ||
+ qdisc_qlen(txq->qdisc) > high) {
+
+ pr_debug("queue stop(%d) or full (%d>%d) - XOFF\n",
+ netif_queue_stopped(caifd->netdev),
+ qdisc_qlen(txq->qdisc), high);
+ caifd->xoff = 1;
+ /* Hijack this skb free callback function. */
+ skb_orphan(skb);
+ skb->destructor = caif_flow_cb;
+ caifd->layer.up->
+ ctrlcmd(caifd->layer.up,
+ _CAIF_CTRLCMD_PHYIF_FLOW_OFF_IND,
+ caifd->layer.id);
+ }
+ }
err = dev_queue_xmit(skb);
if (err > 0)
--
1.7.0.4
--
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